The present invention generally relates to a thermal transfer printer and more particularly, to a supply arrangement of a thermal transfer ribbon for a serial thermal transfer printer so arranged that a carriage detachably mounted with a thermal transfer ribbon cassette is subjected to a horizontal scanning with respect to a recording paper. The thermal transfer printer is capable of selectively effecting a transfer recording onto plain paper through mounting of the thermal transfer ribbon cassette, or a recording onto a heat sensitive paper without mounting the thermal transfer ribbon cassette.
Conventionally, in the thermal transfer printer as referred to above, it has been so arranged that the thermal transfer ribbon fed out from a supply spool is brought into pressure contact with the recording paper between a thermal head and the recording paper. The thermal transfer ribbon is subsequently wound onto a winding spool which is engaged with a scanning mechanism of a carriage for rotation to take up the thermal transfer ribbon thereon. There have not been provided means for detecting the presence or absence of the thermal transfer ribbon, or means for controlling heat generating temperatures for the thermal head according to the result of the detection by the detecting means.
In the known thermal transfer printer as described so far, however, since the carriage motor serves as a driving source for the displacement of the carriage and also for winding the thermal transfer ribbon, the load becomes undesirably large, with a consequent requirement for a motor of a large size. Moreover, the engaging mechanism between the scanning mechanism of the carriage and the winding spool tends to be complicated, and readjustments are frequently required by the characteristic changes of mechanical elements such as springs, wires, etc. through operations for long periods of time. Meanwhile, in the prior art thermal transfer printer as described above, since the thermal transfer ribbon winding means is not required to be driven during recording onto the heat sensitive paper, it becomes necessary to provide means for releasing engagement thereof with the carriage scanning means, thus also resulting in a further complication of the engaging mechanism. Besides, since no means are provided for controlling heat generating temperatures of the thermal head through detection of whether or not the thermal transfer ribbon is attached, there has been such a problem that it is difficult for the thermal head to achieve a proper temperature during either one of the thermal transfer print mode or the recording mode using heat sensitive paper, or during both of these modes.
Furthermore, in the conventional thermal transfer printer, owing to the arrangement that the transfer ribbon winding means is rotated through engagement with the scanning mechanism driven by the carriage motor, upon stopping displacement of the carriage according to the completion of recording, the transfer ribbon winding means stops rotating, and in this case, if the winding of the transfer ribbon is suspended before completion of spacing of the thermal head from the recording paper, the transfer ribbon tends to be loosened or slackened when the thermal head has been completely spaced from the recording paper.
Another disadvantage inherent in the known thermal transfer printer is such that, since it is so arranged that a pressure contact mechanism of the thermal head is driven at the start of the recording so as to bring the thermal head into pressure contact with the recording paper, and thereafter, the carriage motor is driven to displace the carriage, with the transfer ribbon winding means being rotated by said carriage motor, the winding of the transfer ribbon is effected after completion of the pressure contact of the thermal head, but is not effected during functioning for the pressure contact of the thermal head, and thus, slackening of the transfer ribbon takes place in this case also.